In an automotive application, for example, an interface may be required between a sensor block detecting tire pressure and temperature mounted on a wheel and a signal conditioning block mounted on a vehicle for ultimate display of pressure and temperature to a driver. In this example of a rotating wheel, since direct connection is impossible, it is apparent that the signal interface between functional block must be via a coupled path. Hence, the wheel mounted interface circuit must provide the drive for such coupling. Also in such a remote sensing operation energy will be required to power the sensors and hence it is desirable that an energy transfer path is provided if the use (and thereby the replacement) of batteries is to be avoided.
U.S. Pat. No.4,737,761 issued to Dosjoub, describes a system wherein a transmission path is provided by two coils and inductive coupling therebetween. In one arrangement, a single path is used both for power transfer to a sensor block by transformer action and for return transmission of sensor related signals by means of coupled times pulses. Dosjoub provides an interface circuit comprising a four diode bridge rectifier arranged to charge a capacitor to provide a power supply for a sensor block. Dosjoub further provides means in the form of additional components connected across one of the bridge limbs for discharging a capacitor into the wheel mounted coil to cause a return pulse to the stationary coil, the timing of the pulses being the information content of the signal.
In such a remote sensing arrangement, it is desirable that power consumption at the sensing end be minimized. Integration of an interface circuit would achieve this, particularly if sensor block components were integrated in the same device; integration implies lower power consumption since the distances between circuit components is minimized. Integration also provides a physically small arrangement, which is advantageous in space critical applications, including a wheel mounted block.